How can I make the texture gradient?
You can use a gradient texture in the node editor to determine the color. In the node setup in the photo, I am using a gradient texture with generated coordinates. I then rotated it to the correct axis with the mapping node, and also scaled it for a better effect. I then plugged the output of the gradient in a color ramp node, setting black to brown and white to green, giving the color scheme you want. Hope this helps!